It is frequently necessary or desirable to deliver power from a source to aircraft which are at terminal parking positions, in a hangar, or in repair shops or test facilities. Most aircraft are equipped with power input connectors which commonly consist of a male plug recessed for protective purposes in a socket. A suitable female connector head to which a cable from the power source is attached is plugged into the socket when power is needed in the aircraft. Inevitably, the power cable and connector head are subjected to considerable abuse from dragging abrasion or falls against concrete or asphalt surfaces, as well as exposure to petroleum products and weather conditions.
Power delivery systems currently in use often include multiple single conductors banded together at spaced points and individually connected to contact members in the connector head. Such banded conductor assemblies are heavy and cumbersome and require manual wrapping and coiling at the gateway or at the power supply vehicle because they do not lend themselves to proper coiling on a take-up reel. Also, these 5 early connectors lacked any switching capabilities which meant
that they had to be plugged into the planes "live" or, after plugging in, the operator had to walk to the power source where switches were located to turn on power. The absence of switches at the connector head end, further made it impractical to enjoy the convenience and saving of labor that may be had with powered cable reels.
Finally, connector contact members tend to lose their gripping force with use and the passage of time. Ultimately, the weight of the cable and the diminished cable gripping forces combine to cause the connectors to drop out of the aircraft sockets and to fall to the hard surfaces below causing loss of power as well as damage to the connector nose area. Necessary repairs or replacements could be made usually only by the installation of entirely new equipment, field repair not being feasible.